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961.
Yuri Trakhinin 《Archive for Rational Mechanics and Analysis》2009,191(2):245-310
We prove the local-in-time existence of solutions with a surface of current-vortex sheet (tangential discontinuity) of the
equations of ideal compressible magnetohydrodynamics in three space dimensions provided that a stability condition is satisfied
at each point of the initial discontinuity. This paper is a natural completion of our previous analysis (Trakhinin in Arch Ration Mech Anal 177:331–366, 2005) where a sufficient condition for the weak stability of planar current-vortex
sheets was found and a basic a priori estimate was proved for the linearized variable coefficients problem for nonplanar discontinuities.
The original nonlinear problem is a free boundary hyperbolic problem. Since the free boundary is characteristic, the functional
setting is provided by the anisotropic weighted Sobolev spaces . The fact that the Kreiss–Lopatinski condition is satisfied only in a weak sense yields losses of derivatives in a priori
estimates. Therefore, we prove our existence theorem by a suitable Nash–Moser-type iteration scheme. 相似文献
962.
963.
Sergiy Ryabov Nina Kotelnikova Yuri Kercha Svetlana Laptiy Raisa Gaiduk Ludmila Kosenko Alexandra Yakovenko 《Macromolecular Symposia》2001,164(1):421-428
A series of composites based on segmented polyurethanes (PU) as polymer matrices and natural polysaccharides – cellulose and starch – as fillers have been synthesized. Using IR method and Differential Scanning Calorimetry the peculiarities of the structure of composites and their behavior in the buffer solutions in conditions imitating natural soil environment have been investigated. 相似文献
964.
965.
Alexander N. Chernega Alexander V. Ruban Vladislav D. Romanenko Leonid N. Markovski Anatoly A. Korkin Mikhail Yu. Antipin Yuri T. Struchkov 《Heteroatom Chemistry》1991,2(2):229-241
Effets of pπ pπ conjugation in phosphaalkenes have been considered by taking into account the results of X-ray structural studies and ab initio quantum-chemical calculations. The structural consequences of the conjugation depend to a certain extent on the character of the substituent and the place of its attachment to the double PC bond. Depending on the location of the substituent, bond polarization may strengthen or weaken (compensate for) the conjugation effects. A high contribution of the s-character of the lone electron pair of the P atom is an essential feature of the electron structure of a phosphaalkene. 相似文献
966.
Kseniya N. Sedenkova Kristian S. Andriasov Marina G. Eremenko Yuri K. Grishin Vera A. Alferova Anna A. Baranova Nikolay A. Zefirov Olga N. Zefirova Vladimir V. Zarubaev Yulia A. Gracheva Elena R. Milaeva Elena B. Averina 《Molecules (Basel, Switzerland)》2022,27(11)
The application of non-planar scaffolds in drug design allows for the enlargement of the chemical space, and for the construction of molecules that have more effective target–ligand interactions or are less prone to the development of resistance. Among the works of the last decade, a literature search revealed spirothiazamenthane, which has served as a lead in the development of derivatives active against resistant viral strains. In this work, we studied the novel molecular scaffold, which resembles spirothiazamenthane, but combines isoxazoline as a heterocycle and cyclooctane ring as a hydrophobic part of the structure. The synthesis of new 3-nitro- and 3-aminoisoxazolines containing spiro-fused or 1,2-annelated cyclooctane fragments was achieved by employing 1,3-dipolar cycloaddition of 3-nitro-4,5-dihydroisoxazol-4-ol 2-oxide or tetranitromethane-derived alkyl nitronates with non-activated alkenes. A series of spiro-sulfonamides was obtained by the reaction of 3-aminoisoxazoline containing a spiro-fused cyclooctane residue with sulfonyl chlorides. Preliminary screening of the compounds for antiviral, antibacterial, antifungal and antiproliferative properties in vitro revealed 1-oxa-2-azaspiro[4.7]dodec-2-en-3-amine and 3a,4,5,6,7,8,9,9a-octahydrocycloocta[d]isoxazol-3-amine with activity against the influenza A/Puerto Rico/8/34 (H1N1) virus in the submicromolar range, and high values of selectivity index. Further study of the mechanism of the antiviral action of these compounds, and the synthesis of their analogues, is likely to identify new agents against resistant viral strains. 相似文献
967.
Yuri G. Figueiredo Eduardo A. Corrêa Afonso H. de Oliveira Junior Ana C. d. C. Mazzinghy Henrique d. O. P. Mendona Yan J. G. Lobo Yesenia M. García Marcelo A. d. S. Gouvêia Ana C. C. F. F. de Paula Rodinei Augusti Luisa D. C. B. Reina Carlos H. da Silveira Leonardo H. F. de Lima Júlio O. F. Melo 《Molecules (Basel, Switzerland)》2022,27(5)
968.
969.
The present work applied the methods of density functional theory and the van der Waals interaction PBE + D3(BJ) on the basis of localized orbitals of the CRYSTAL17 package. It featured the effect of interactions between structural elements of fluorocarbonates ABCO3F (A: K, Rb, Cs; B: Mg, Ca, Sr, Zn, Cd) on their elastic and vibrational properties. The hexagonal structures proved to consist of alternating ···B-CO3··· and ···A-F··· layers in planes ab, interconnected along axis c by infinite chains ···F-B-F···, where cations formed polyhedra AOnF3 and BOmF2. The calculations included the band energy structure, the total and partial density of electron states, the energy and band widths of the upper ns- and np-states of alkali and alkaline-earth metals, as well as nd-zinc and nd-cadmium. For hydrostatic compression, we calculated the parameters of the Birch–Murnaghan equation of state and the linear compressibility moduli along the crystal axes and bond lines. We also defined the elastic constants of single crystals to obtain the Voigt–Reuss–Hill approximations for the elastic moduli of polycrystalline materials. The study also revealed the relationship between the elastic properties and the nature of the chemical bond. Hybrid functional B3LYP made it possible to calculate the modes of normal long-wavelength oscillations, which provided the spectra of infrared absorption and Raman scattering. Intramolecular modes ν1 and ν4 with one or two maxima were found to be intense, and their relative positions depended on the lengths of nonequivalent C–O bonds. 相似文献
970.
Anton A. Ulantikov Konstantin A. Brylev Taisiya S. Sukhikh Yuri V. Mironov Viktoria K. Muravieva Yakov M. Gayfulin 《Molecules (Basel, Switzerland)》2022,27(22)
A series of eight new octahedral rhenium cluster complexes with the general formula trans-[{Re6Q8}L4X2] (Q = S or Se; L = 1,2-Bis(4-pyridyl)ethylene (bpe) or 1,3-Bis(4-pyridyl)propane (bpp); X = Cl or Br) was synthesized and investigated. While bpe is a ligand with a conjugated aromatic system, bpp represents a molecule of opposite type and has independent aromatic systems of the two pyridine rings. It was shown that this difference in the electronic structure of the ligands has a fundamental effect on the electronic structure, electrochemical and luminescent properties of the corresponding cluster complexes. Specifically, the [{Re6Q8}(bpe)4X2] complexes in solutions show multiple quasi-reversible electrochemical transitions associated with reduction of the organic ligands. At the same time, the trans-[{Re6Q8}(bpp)4X2] complexes show multielectron quasi-irreversible reduction processes, which correlate with the mixed character of the lowest unoccupied molecular orbitals of these complexes. All the obtained new compounds exhibit red photoluminescence. The photophysical parameters (emission lifetimes and quantum yields) measured for the bpp complexes exceed those revealed for bpe complexes by more than an order of magnitude. 相似文献